Covid-19 / Public Health / Health
The Science Behind Contact Tracing, and the Limitations to US Implementation
Privacy concerns and the role of government could impede a key facet of US pandemic tracing
In any given day, people interact with one another countless times. Even seemingly non-interactions — sitting next to a stranger on the bus, for example — count as contact when it comes to tracing the spread of an outbreak. It is this fact that has public officials concerned with the rapid proliferation of Covid-19. But, for epidemiologists trained to chart the course of a disease, mapping an individual’s many contacts with other people — what is known as contact tracing — is a powerful tool in tracing the origin of a disease as well as implementing appropriate social isolation guidelines.
Disease tracing as an exact science dates back to the mid-1800’s when an outbreak of cholera ripped through the SoHo district of London. A local physician, John Snow, began to objectively map the location of new cases of cholera. By interviewing families and tracing their behaviors, he was able to identify the source of the outbreak, the now famous Broad Street pump, a public water pump where locals went to collect drinking water. John Snow was able to persuade the city to close down the pump and soon the outbreak of cholera subsided. Dr. Snow’s achievement marked a turning point for what we now know to be modern public health and epidemiology. Much of this achievement rested on the practice of contact tracing.
Flash forward to late 2019 as the first cases of Covid-19 began popping up in Chinese hospitals. As the disease spread rapidly to other countries, it became immediately apparent that this disease was highly transmissible and posed a serious threat for a global pandemic. The differing actions taken by countries touched by the pandemic resulted in vastly different outcomes in both new cases and deaths from Covid-19. As reports of new cases began to emerge from different regions of the globe, South Korea stood out as a coutnry that had rapidly curtailed the spread of coronavirus.
The key to South Korea’s success early in the coronavirus outbreak came down to a few key actions including early labeling of the pandemic as an urgent threat, rapid roll-outs of testing kits, and contact tracing. Once a person was confirmed positive for Covid-19, their behaviors and interactions were closely traced so as to find any possible contacts that person may have had. Given the relatively long infectious incubation period when people are still able to transmit the disease, the task of tracing contacts was a huge effort. But, through this officials were able to successfully isolate people who had confirmed contact with an infected person. Officials relied on data from GPS systems built into phones, payment histories on credit cards, and other metrics that could help create a map of individuals that infected people came into contact with. Once this map of contacts was made, people who had exposure with this individual were contacted and instructed to go into isolation.
Contact tracing resembles the methods employed by John Snow in 1855, where people are directly interviewed and asked about their movements and interactions with others. With this, researchers go on an interview hunt seeking to find those who came into contact with an infected person, recommending their isolation and further tracing their movements to seek out further contacts. This approach is labor intensive and time consuming, requiring people to individually go out and interview everyone who may have come into contact with an infected person. With new cases quickly ballooning in affected countries, this presents a massive public health challenge.
Successful contact tracing relies on broad testing for positive cases, something that many countries lagged behind on early in the outbreak. South Korea was successful in implementing testing by rushing to release hundreds of thousands of test kits and to provide sites where the public could be tested while countries like the US were slow to respond. Without accurate testing to confirm cases of Covid-19, contact tracing is no better than searching in the dark for possible infected people.
Modern contact tracing relies on technology, with potentially the most valuable tool for tracing human behavior held in one’s hand. Cellphones rely on GPS data for apps that provide directions or location information. GPS can provide a map of a persons whereabouts in real time. Likewise, Bluetooth embedded in most phones relies on close contact between devices, and also provides a tool for determining whether a person “contacted” another. Also, phones and social media provide an avenue for rapid contact an dissemination of information, which theoretically provides officials a tool for immediately alerting persons of a risk for infection. These tools were all used by the South Korean government to apparent success. The use of technology also potentially eases the burden of in-person interviewing. But, this level of aggressive public health effort raises concerns for privacy and the role of government in many countries, particularly the US.
Privacy, as it pertains to the use of cell phone usage data is an issue that concerns most Americans. As companies grow ever-willing to extract and use data on travel, shopping and social habits for advertising purposes, people become wary of these practices. These practices concern many US citizens as they feel that their habits and behaviors are not public information, or information that should be sold for economic gain.
The contact tracing methods used by the South Korean government relied on location data from devices to trace infected people’s interactions. To do so, alerts were sent out to people at risk of possible infection that included identifying information about the infected person. This raises concerns about privacy of health information as well as the safety of individuals that would make these practices hard to implement in other countries.
Europe is in the process of implementing a system for contact tracing that relies on Bluetooth and GPS data along with complex algorithms to trace contacts between people. The Pan-European Privacy-Preserving Proximity Tracing (PEPP-PT) seeks to utilize Bluetooth data from individuals devices, while providing anonymity and privacy protection. Because Bluetooth relies on proximity of devices, it is more reliable in confirming a possible contact (GPS data is not always accurate enough to confirm that two devices were within the 6' distance that constitutes a “contact”). Germany is adopting this program and hopes to have it rolled out by mid-April.
In the US, there are limitations on how the government can monitor phone data, which often requires a court order. Despite that, the US government has the capability and does monitor individuals cell phone data. Many US citizens feel that this is an over-reach of government and oppose these practices. Fears that the government had stepped up surveillance of cell phones in the years that followed the 9/11 attacks made this issues even more prominent in the public eye. The willingness of people to allow themselves to be traced poses a large hurdle to putting these practices in place.
Public Buy In
For the US to employ a broad contact tracing program that relies on technological data, it would not only require swift and accurate testing for Covid-19, but a huge public buy in. For a program to be successful, people would need to voluntarily download an app and allow for it to transmit specific data pertaining to their movements and proximity to other devices, trusting that the data would remain anonymous and their privacy preserved. To achieve this would require a level of public unity around how to address a problem like Covid-19 that is not universally present in the US today. Successful contact tracing would require public trust in a nation-wide effort to stop the spread of coronavirus.
Only adding to these difficulties is the fact that current policies and actions are determined by individual states rather than the federal government. With the current administration quick to preserve the power of the states, it makes a nation-wide contact tracing effort difficult to implement.
Many people in the US are wondering when they can return to life as normal. The impacts of social distancing and isolation are having impacts on the economy, jobs, education and mental health. The longer the public is required to adhere to social distancing, the longer these impacts will be felt. But without a clear indication that the spread of coronavirus has slowed, it would be irresponsible for officials to lift these restrictions as they would likely only require a spike in new cases and even prolonged restrictions.
Contact tracing as a tool within a broader public health effort against Covid-19 would offer officials a way to isolate confirmed cases and those who have been in contact in selective way, allowing the return to a semi-normal way of life. Without a unified effort and broad public support, this practice will face huge challenges to be successful, particularly in the US. The US would benefit from using the examples of the successful public health practices from countries like South Korea to build a unified national response system, if not for the current Covid-19 outbreak, but for any and all future pandemics.